Track chains · Pitch and machine class, dry, greased or sealed-and-lubricated joints, rail and pin hardness, master pin fit, pitch extension from pin and bushing wear, sprocket matching
A track chain is the linked steel backbone of a crawler undercarriage, made of forged and heat-treated link pairs joined by hardened pins and bushings (dry, greased or oil-filled and sealed), on which the track shoes are bolted and which the sprocket drives around the idler and rollers. Ask three things first: the pitch, link count and machine model it must fit, which joint type and hardness suit the work, and how wear will be measured against the sprocket.
Track chains (track links with pins and bushings) and assembled track groups for excavators, dozers and other crawler machines. Track shoes, rollers, idlers and sprockets sold alone, rubber tracks and conveyor or roller chains are outside this page.
01
Astrak, a UK undercarriage supplier, offers excavator track chains from 101 mm to 260 mm pitch for 3 to 80 tonne machines: dry chains up to 135 mm pitch for mini and midi excavators, and greased chains, grease filled and sealed with polyurethane seals, from 140 mm upward, including 171 mm (around 13 t), 190 mm (around 20 t), 228 mm (around 50 t) and up to 260 mm for quarry machines up to 80 t. 101.6 mm chains come as track groups with shoes welded on. [1]
For dozers it supplies sealed and lubricated track (SALT) chains, oil filled to cut internal friction between pin and bushing, which it says extends internal bushing life by up to 50% compared with greased and sealed chains; Astrak gives greased chains 20–30% (typ.) longer life than dry ones. Master pins are easy fit as standard, or press fit (matching the other pins, requiring a track press) on 171 and 190 mm pitch chains. [1]
Editorial note: specify the original machine model and serial range, pitch, number of links, master-link type and shoe bolt pattern; pitch alone does not guarantee fit.
Give the supplier the machine make, model and serial range, pitch, number of links, joint type (dry, greased, SALT), master pin or master link type, rail height and heavy-duty options, track shoe type and bolt pattern if supplying a track group, hardness and heat-treatment requirements, operating conditions (abrasive, rocky, wet) and quantities.
02
Astrak's chain rails are heat-treated boron steel hardened to 48–56 HRC up to 10 mm deep, and all pins and bushes are hardened to 55–60 HRC. It says wear should be checked against the new chain specification, and that on a 50-link chain 1 mm of pin wear plus 1 mm of bush enlargement adds around 100 mm to overall length. [1]
Komatsu explains that on a new machine the link pitch (centre distance between pins) equals the sprocket pitch; with use, the sprocket pitch shortens slightly as tooth surfaces wear while the link pitch extends as pin outer diameters and bushing bores wear, and running on with the mismatch causes abnormal wear of the bushing outer diameter and sprocket teeth, shortening sprocket life. [2]
Editorial calculation: 2 mm of combined pin and bushing wear per joint on a 190 mm pitch chain extends each pitch by about 1.1% (2 ÷ 190); over 50 links that is the 100 mm Astrak describes. Agree with the supplier how pitch will be measured over a stated number of links and what extension triggers replacement. [1] [2]
Rail hardness need not be uniform along the link. Caterpillar's European patent EP 3 849 887 B1 (priority 2018) describes a track link whose upper rail wear band varies in hardness lengthwise to retard scalloping, the uneven wear caused by sliding contact with idlers. The link body is heat-treated and quenched to a hardness greater than 50 HRC (about 55 HRC or greater), then selected zones of the rail are tempered to below 50 HRC (about 45 HRC or less), leaving a harder zone that covers about 20% or less, and potentially about 10% or less, of the rail length within each link strap; the softened troughs reach about 50% or less of the depth of the hardened boundary below the rail surface. [4]
Editorial calculation: in the patent the hard and tempered zones differ by more than 5 HRC (above 50 HRC against about 45 HRC or less), so a single quoted range such as Astrak's 48–56 HRC does not show whether hardness varies along the rail; ask the supplier where along the link its rail hardness figure applies. [1] [4]
03
US patent 8,070,241 B2 (Deere & Company, priority 2009), Track chain joint with rotatable pin, describes a dozer track joint built as a cartridge: a freely rotatable solid pin, a bushing journalled on the pin and fixed to the inner links, collars fixed to the outer links, drive caps fixed to the pin that engage a dual sprocket, and annular inboard and outboard seals, assembled and sealed to hold lubricant before it is joined to the links. [3]
The patent states that moving the reservoir into the bushing allowed a larger volume (for example, doubled) and that a secondary channel can be used to flush lubricant from the cartridge. This shows what lies behind the dry, greased and sealed chain types described above: ask how the joint retains its lubricant and whether it can be refilled. [3] [1]
Editorial calculation: ±0.002 in is about ±0.05 mm on a 293 mm pin, a tolerance of about 0.02%.
| Joint feature (US 8,070,241) | Detail given |
|---|---|
| Lubricant | Oil such as 80W90, held in an annular reservoir in the bushing bore |
| Fill | Channel from bushing outside to reservoir, closed by a 1/8 in NPT steel plug |
| Pin | Solid, no drilled lubricant channel, removing a stress concentration and the plastic plug and grommet |
| Example pin length | 293.00 mm, tolerance ±0.002 in, to set sealing of the cartridge |
| Bushing fixing | Interference fit to the links, adding torsional rigidity that resists lubricant leakage |
| Sprocket contact | Rotatable drive caps engage the sprocket teeth, spreading joint load |
State the machine and duty, and ask whether the chain is dry, greased or sealed-and-lubricated, how lubricant is held and refilled, seal type, and the pin and bushing design (rotating or fixed).
04
Listings include excavator and dozer track chains, track links, track groups and track chain assemblies alongside other undercarriage parts.
05
| Part | Role | Fix in the order |
|---|---|---|
| Links (rails) | Carry rollers; form the chain. [1] | Material, hardness, rail height. |
| Pins | Join links. [1] | Hardness; master pin type. |
| Bushings | Engage the sprocket. [2] | Hardness and diameter. |
| Seals and lubricant | Keep grit out; reduce wear. [1] | Dry, greased or SALT. |
| Master pin or link | Opens the chain. [1] | Easy or press fit. |
| Sprocket match | Equal pitch when new. [2] | Replace together if worn. |
06
Pitch and link count decide fit, and pitch tolerance decides how the new chain meets the sprocket; hardness and joint lubrication decide how long it holds that pitch.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Pitch (mm) | 101–260 mm across one range. [1] | Pitch and link count. |
| Track Width (mm) | Set by shoes. | Shoe width. |
| Tensile Strength (MPa) | Link and pin strength. | Value and test. |
| Hardness (HRC) | Rails 48–56; pins and bushes 55–60 in one range. [1] | Hardness and depth. |
| Operating Temperature (°C) | Seal limits. | Range. |
| Weight per Meter (kg/m) | Handling. | Weight. |
| Bushing Diameter (mm) | Engages sprocket. [2] | Diameter. |
| Pin Diameter (mm) | Joint size. | Diameter. |
| Track Link Height (mm) | Wear allowance on rail. [1] | Height; heavy-duty option. |
| Grouser Height (mm) | On shoes. | Height. |
| Material Grade | Boron steel rails in one range. [1] | Steel grade. |
| Tolerance on Pitch (mm) | Matches sprocket when new. [2] | Tolerance and method. |
| Joint lubrication | Sealed cartridge with oil reservoir in the bushing, refillable through a plug (US 8,070,241). [3] | Joint type and refill method. |
| Rail hardness pattern | Hardened above 50 HRC then zones tempered to about 45 HRC or less, harder zone about 20% or less of rail length, in one Caterpillar patent. [4] | Hardness map along the rail and case depth. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Machine: [make; model; serial range] Chain: [pitch; links; master pin] Joint: [dry; greased; SALT] Material: [hardness; rail height] Group: [shoe type; width; bolts] Supply: [conditions; warranty; quantity]
Quanzhou Zhongkai Machinery lists track links and track groups for dozers and excavators. Xiamen Doolin, Xiamen Fortune, Xiamen Yintai, XMGT, Quanzhou Juli and Luoyang Reliable list track chains next to rollers, idlers and sprockets, and Yantai Chicheng lists them with hydraulic parts.
Lists track links and track groups among dozer and excavator undercarriage parts.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among undercarriage parts such as rollers, idlers and sprockets.
Product scope checked 2026-10-11
Lists track chains among hydraulic and undercarriage parts.
Product scope checked 2026-10-11
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Astrak gives greased chains 20–30% (typ.) longer life than dry chains, and says SALT chains extend internal bushing life by up to 50% over greased chains. [1]
Astrak notes 1 mm of pin wear plus 1 mm of bush enlargement adds about 100 mm to a 50-link chain. [1]
Komatsu explains that worn chain pitch no longer matches the sprocket, causing abnormal wear on bushings and sprocket teeth. [2]
In one Deere patent, oil such as 80W90 sits in an annular reservoir in the bushing bore, filled through a channel closed by a 1/8 in NPT plug, with inboard and outboard seals. [3]
Caterpillar's patent EP 3 849 887 B1 describes scalloping as rail wear from sliding contact with idlers and resists it by varying rail hardness along the link: above 50 HRC in a harder zone covering about 20% or less of the rail, tempered to about 45 HRC or less elsewhere. [4]
Sources checked 2026-10-12. Astrak describes its own chain range, Komatsu explains undercarriage wear, and Deere and Caterpillar patents describe their own joint and link designs; dimensions and limits for your chain must come from the machine maker's data and the supplier.
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